1. Field of the Invention
The present invention relates to a distributed type of on-vehicle control system in which a plurality of electronic control programs communicate with each other on messages and responses transmitted and sent thereamong, and in particular, to an apparatus for administrating the messages and responses transmitted and sent among the plurality of control programs.
2. Description of the Related Art
Recently many vehicles are full of electronic devices, which require a control system to control such electronic devices. One type of such control systems is a distributed type of control system with a plurality of application components (hereinafter abbreviated as “APs”) assigned to each function necessary for driving a vehicle.
Specifically, “AP” is a control program (also called “application program”) to achieve an objective function, and, in detail, is software consisting of program codes composing a control program and data referred while the control program is executed. In the present specification, for the sake of convenience, an expression whose subject is a program, such as “AP does . . . ,” is used in some occasions. Such an expression means the performance of functional means achieved by the CPU's execution, or more simply, by contents of the function of the program.
In this kind of control system for vehicles (on-vehicle control system), a plurality of APs work together using messages communicated among the application components, whereby each predetermined function for driving a vehicle is achieved. For example, when some AP sends a requesting message to request another AP to carry out a certain process, the AP which receives the requesting message carries out a corresponding process to the requesting message and sends back the processing result.
In terms of a hardware configuration, each AP is mounted in a separate electronic control unit (ECU), the plurality of ECUs communicate each other via a network build in the vehicle. This is, for example, set forth in Japanese Patent Laid-open (unexamined) No. 2001-270399. As another type, respective APs are mounted in one ECU, in which messages and correspondences are exchanged in the ECU.
In the known on-vehicle control systems one of which is disclosed in the above reference document, it is preferred that the systems are able to carry out a process, called “deadline monitor.” This process is prepared for monitoring whether or not a process requested by a message issued from one AP has been completed within a preset period of time. However, in the known on-vehicle control systems, an amount of processing load to perform the deadline monitor is forced to rise.
Simply, the reason is that, since the response-waiting message is searched among all request messages by checking the message status of each of all request messages recorded in the message information administration table, some process is executed to messages which are not issued from an AP, thus not waiting for responses. This reason will be exemplified later in detail together with the description of the preferred embodiment.